How would you clean this mesh up?
ALT select edges in Edge Mode, and X - dissolve.



Update: In response to your Sub-div issue. Instead of just removing geometry, you might look at how you are modeling. In the example below I have made the windows edge loops. The one on the left is all quads, and the one on the right has one N-gon in the window - if you don't mind N-gons. The advantage of this geometry can be noted on the sides [top &amp; bottom] where less faces are needed.